He is the founder and head of design for Thom Browne, a luxury fashion brand based in New York City.

[10][5] Browne started making custom suits after befriending Johnson Hartig, who went on to found the brand Libertine.

[13] The brand's first external investor, Japan's Stripe International (formerly Cross),[14] gave the company the capital it needed to recover from the 2007–2008 financial crisis, before selling its stake on to Sandbridge Capital – a private equity firm whose advisors included Tommy Hilfiger, Domenico De Sole and Dominique de Villepin –[15][14] in 2016.

In July 2008, Thom Browne and Brooks Brothers announced they would continue their partnership in the Black Fleece collection for another three years.

Brooks Brothers opened a standalone Black Fleece store located in New York City's West Village.

[29] His designs are both classic and subversive, rooted in the gray suit but transformed into fashion statements through unconventional cuts, proportions, and androgynous detailing.

[30] Browne frequently explores the concept of the "uniform", with his collections adhering to a strict aesthetic code while allowing for personal expression within the structure.

[11] In 2018, LeBron James led the entire Cleveland Cavaliers team during the NBA playoffs in coordinated gray Thom Browne suits.

[38] A jury determined in 2023 that the Thom Browne designs were not likely to cause customer confusion with Adidas' products and did not violate the company's trademark rights.

[38] Browne lives with partner Andrew Bolton,[39] who is curator at the Costume Institute of the Metropolitan Museum of Art in Manhattan.

In 2019, Browne and Bolton purchased and renovated a 7,000-square-foot, 15-room Sutton Place mansion formerly owned by the philanthropist Drue Heinz.